None of us wants to leave an open court; a spot that the other team can attack
and beat us. Let's look at three rules to help you close the angles. The illustrations below may help you better grasp the concepts.
The most important angle to close off is the middle of the court. Do what you
have to do to make sure your opponents cannot attack you down the middle. This is, by far, the largest and safest angle for your opponents to attack.
2 - Next depends on position
If one team is at the baseline (not at the NVZ) and the other is at the NVZ,
the most important angle to close down is the down the line (straight) angle.
If both teams are at the NVZ, the most important angle will depend on your
opponents and the flow of the point, but generally will also be the down the line
(straight) angle. You may, however, have to adjust to weight your coverage to the
cross court angle. When in doubt, close down the down the line shot.
You closed down the two largest pieces of the court yet your opponent still
passes you on the small angle, then: (a) do not stress about it and (b) put it into the thinkometer (brain) to determine if you need to change angle closures. But still do not stress about it.
The reality is that there is always going to be an open angle on the court. Your job? Make the open angle as small (and thus, as difficult to hit) as possible. Do not stress if the other team finds an opening - as long as the opening is the smallest one you could leave open.